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Effect of induced tolerance to B t toxin on the egg size of H elicoverpa armigera and parasitism by T richogramma pretiosum
Author(s) -
Anantanawat Kay J.,
Glatz Richard,
Keller Michael A.
Publication year - 2016
Publication title -
physiological entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.693
H-Index - 57
eISSN - 1365-3032
pISSN - 0307-6962
DOI - 10.1111/phen.12152
Subject(s) - biology , helicoverpa armigera , parasitism , host (biology) , larva , offspring , parasitoid , toxin , pest analysis , botany , microbiology and biotechnology , ecology , genetics , pregnancy
Larvae of H elicoverpa armigera ( H übner) can develop a form of B t tolerance after exposure to sub‐lethal doses of B t ‐toxin subclass Cry1Ac . Increasing levels of tolerance are produced over generations of larval exposure, which are not related to DNA sequence changes, and are largely maternally transmitted. The characteristic of maternal transmission, combined with the importance of egg parasitoids to cotton pest management, raises questions about the effects of B t tolerance/exposure on the eggs of H . armigera and on some key metrics of egg parasitism. In the present study, the effect of inducible tolerance on eggs of H . armigera and parasitism by T richogramma pretiosum ( R iley) is investigated. First, the volumes of eggs laid by susceptible and tolerant H . armigera females are compared. In addition, the effect of inducible tolerance on egg parasitism is determined by comparing parasitism success, the number of adult wasps emerged per host egg, and the proportion of male and female offspring emerged per host egg. The results obtained suggest that Cry1Ac ‐tolerance is associated with increased egg volume, even after just one generation of sub‐lethal exposure. When tolerant H . armigera are freed from ongoing sub‐lethal exposure, a corresponding decrease in egg volume is not detected. Although there is no difference in the percentage of eggs parasitized, there is an increase in the number of emergent parasitoids, especially males, from eggs laid by tolerant H . armigera . These results confirm that maternally‐transmitted B t tolerance is reflected in the phenotype of the eggs of tolerant offspring, which affects egg parasitism.